ASA 107, Celestial Navigation

ASA 107, Celestial Navigation

Able to apply celestial navigation theory and practices for safe navigation of a sailing vessel in offshore waters. On-water celestial navigation skills elements are demonstrated in ASA 108, Offshore Passagemaking.

Prerequisites and the ability to demonstrate competencies in all knowledge and skills elements of that Standard.
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ASA 107, Celestial Navigation Standards


1. Convert longitude into time.

2. Convert standard time and zone time to GMT and vice versa.

3. Calculate the zone time given longitude.

4. Calculate the chronometer (or watch) error given a previous error and the daily rate.

5. Apply the corrections for index error, dip of the horizon, and total correction to convert sextant altitudes of the sun, stars, planets, and moon to true altitudes.

6. Calculate the time of meridian passage of the sun and calculate the boat’s latitude from the observed meridian altitude of the sun.

7. Determine the latitude at twilight by means of the Pole Star.

8. Solve the navigational triangle using a navigation table and show all appropriate work.

9. Plot celestial lines of position on a Mercator projection or on a universal plotting sheet.

10. Calculate the times (ship’s and GMT) of sunrise, sunset and twilight.

11. Determine the approximate azimuths and altitudes of the navigational stars and planets at twilight.

12. Calculate and plot the lines of position obtained from observations of several celestial bodies at twilight and thus find the boat’s position.

13. Advance the LOP obtained from a sun sight to another LOP obtained from the sun at a later time and find the boat’s position using a running fix (sun-run-sun).

14. Calculate the true bearing of a low altitude celestial body in order to determine the error and deviation of the compass.